Method for producing napthas of improved characteristics from highly refined naphthas by treating the highly refined naphthas with a copper acetate



United States Patent() METHOD FOR PRODUCING NAPTHAS OF IM- PROVEDCHARACTERISTICS FROM HIGHLY REFINED NAPHTHAS BY TREATING THE HIGHLYREFINED NAPHTHAS WITH A COPPER ACETATE Weldon Grant Annable, Mundelein,Ill., assignor to The Pure Oil Company, Chicago, 111., a corporation ofOhio No Drawing. Application April 1, 1954, Serial No. 420,462

7 Claims. (Cl. 196-28) This invention is directed to a method for theproduction of petroleum naphthas characterized by their ability to passthe Distillation-Corrosion test and, more particularly, the inventionrelates to the production of noncorrosive naphtha hydrocarbon bychemical reaction or treatment with an organo-copper compound,particularly solid cupric acetate having the formulae Cu(C2HsO2) 2 H20and basic cupric acetate having the formulae CIl(C2H302) CuO 6H2O at atemperature of about 400 to 500 F.

Crude petroleum has long been the source of widely known productsincluding gasoline, kerosene, diesel fuels, lubricating oils, and heavytars. In many instances, the products obtained from petroleum areemployed as reactants in the synthesis of additional petroleumderivatives and chemicals and a large number of products of petroleumare used directly without extended treatment or modification. Petroleumnaphthas comprise a wide variety of such latter products usedextensively in the dyeing, rubber, extraction, protective coating, andallied industries. A large portion of the petroleum naphthas used is thestraight-run naphthas which are selected fractions of the lower boiling,more volatile constituents of crude petroleum. The present invention isdirected to a method of transforming deleterious sulfur compoundspresent in hydrocarbon mixtures into forms which are less obnoxious andnon-corrosive and will be illustrated by the treatment of straight-runnaphthas. The examples given are not to be construed as limiting theinvention. The term naphthas as used herein shall mean straight-runpetroleum naphthas and other hydrocarbon mixtures or their equivalentscontaining deleterious sulfur compounds which must be transformed tomeet rigid corrosion tests.

Naphthas prepared from petroleum by physical means inevitably containother types of organic and inorganic compounds due to the complex natureof petroleum which are deleterious as far as certain end uses of thenaphthas are concerned and necessitate the application of additionalrefining steps. Even with such additional refining, it is exceedinglydifficult to prepare naphthas which meet the exacting specificationsthat have been established bythe industry. 'Of these deleteriousnon-hydrocarbon compounds, the sulfur and sulfur-containing constituentsare generally the most persistent and cling tenaciously to anyenvironment in which they exist, imparting objectionable odor,corrosiveness, color, and other physical and chemical propertiesthereto. The odor of naphthas is important; however, no standard testexists to cover this property and the odor of a Well refined naphtha isgenerally described as sweet.

Tests have been devised to determine both quantitatively andqualitatively the presence of these odious com- Patented Nov. 6, 1956pounds in an attempt to control the properties and quality of naphthasfrom petroleum sources. For this purpose, various copper strip corrosiontests, the mercury test, the lead acetate test, and the doctor test areused. Procedures established by A. S. T. M. are used to determine thecontent and distribution of these sulfur compounds. Perhaps the mostcritical and rigorous qualitative test for determining the presence ofcorrosive sulfur compounds in naphthas is the distillation-corrosiontest, known also as the Philadelphia test, the Amsco corrosion test, orthe full boiling range corrosion testby any name, a particularlyrigorous species of copper strip corrosion test. The test, widelyapplied by the manufacturers, distributors, and users of specialtynaphthas, is carried out by the addition of a small pure copper couponto an ordinary A. S. T. M. distillation flask containing cc. of thenaphtha to be tested. The copper strip is so positioned in the flaskthat one end of the strip contacts the residue at the end of thedistillation, and the distillation is conducted according to A. S. T. M.D86-38 as described in A. S. T. M. Standards on Petroleum Products andLubricants, published by the American Society for Testing Materials,Philadelphia, Pennsylvania.

At the completion of the test, wherein the flask has been heated todryness, the color of the copper strip is an indication of the relativeamount of corrosive sulfur compounds present in the naphtha sample. Anegative test is shown by the presence of a very slight or moderatetarnish on the strip and stamps the naphtha as satisfactory. If thecopper strip becomes moderately blackened, the results are interpretedas positive or unsatisfactory. The production of a slightly tarnished orslightly colored or corroded strip, indicated by a dark orange withpeacock colorations thereon, is termed borderline and as such denotes anaphtha which is not acceptable and must be further refined. The marketis limited for off-specification naphthas and further refining isexpensive since even then there is no assurance that the product willpass the severe distillation-corrosion test.

The subjection of high sulfur content naphthas to various refining andsweetening operations which may include oxidation and extractionmethods, or the recycling of rejected off-specification naphthas backthrough such a process, does not produce acceptable naphthas because thesulfur compounds remaining are the most difficult to remove and the mostcorrosive. High sulfur content naphthas usually have a poor odor as wellas other undesirable properties. If straight-run naphthas from highsulfur crudes are subjected to other more severe refining methods, theresulting products may pass the other tests for sulfur compounds but donot pass the distillation-- corrosion test. Often naphthas are producedwhich are negative or borderline to the distillation-corrosion test andwhich exhibit a positive reaction to one or more of the other tests forsulfur compounds. Since naphthas must pass all such tests to beacceptable, further treatment is necessary. Prior art methods ofdesulfurization when. applied to such naphas may produce a doctornegative or mercury negative product, but in so doing the end result isa positive distillation-corrosion test.

Accordingly, the primary object of this invention is to overcome thisproblem and provide a process for producing improved naphthas bychemical reaction or treatment with certain copper compounds at 400 to500 F. and preferably at 450 F.

A second object of the invention is to provide a method of producingnaphthas which pass the distillation-corrosion test from naphthascontaining unacceptable amounts of sulfur compounds.

These and other objects of the invention will become apparent as thedescription thereof proceeds.

In the prior art there are described many methods for desulfurizing andsweetening hydrocarbon mixtures.

These" processes may be roughly divided into two" groups-those involvingchemical treatment or adsorptive contact at low temperatures with themain purpose l'ie'ing the removal of free sulfur, hydrogen sulfide, andthose organic sulfur'compounds which may be adsorbed; thesecon'd' groupof processes, which include hydrodesulfurization reactions, areconducted at elevated temperaturesandinvolve the breakdown of the organosulfur compounds into products including hydrogen sulfide. During thesehydrodesulfurization processes, the sulfur compounds. present aresubstantially completely destroyed' and there takes place reactionsinvolving hydrogenation; dehydrogenation; reforming, and the like,depending onthe particular catalyst used and the operating conditions.In general, especially in' the presence of hydrogen under optimumconditions; gasoline products are obtained which have increased octanenumbers and good leadsuscep'tibility. Products produced by these methodsmay have their sulfur contents greatly reduced, and it is not uncommonto reduce the sulfur content to points below20;0l percent sulfur. Theseprior art processes cannot be depended upon. to produce naphthaswhichare non-corrosive to the distillation-corrosion test because the typesof organic sulfiir compounds remaining after theset'reatments arethe'very types. that are corrosive to copper and, though p'resentin' avery small amount, are deleterious and indicate an unsalable' product.Therefore a sharp distinction must bema'debetweenfdesulfuriz ajtiongenerally as" meant inthe prior art and the desulfurization' necessary"to' roduce non-corrosive naphthas; The present invention is directed tothe finding that at a temperature of about 400 to 500 F. solid cupricacetate andbasic cupric acetate or their mixtures-may be used to contactnaphtha hydrocarbons: to transform the sulfur compounds therein to formswhichare nonjcorrosive to thedistillatiomcorrosion test. It'has'b'eenfound that at temperatures below 400 F., although there may be a largedegree of desulfurization, the remaining sulfur compounds are'corrosiveto the distillation-corrosion test. In ordinary gasoline sweeteningpr'ocess'es' using oxidizing agents"; the general'object is toconvertthe mercaptans to disulfides. I At temperatures above about 350 F'., thedisulfides break down and form lesser amounts of corrosive" sulfurcompounds; Thus, because of the insta bility of the disul fides, thesemethodsof desulfurization or sweetening cannot be used to produce sweetnaphthas. This is especially true in. considering crude naphthas whichhave aboveabout 0.003 percent mercaptan's; If th'echemical treatment ordesulfurization' is carried out according to the prior artattemperatures of above 500 Fl, there may be adequate.desulfurigfa'tiori, but' byroniict a re formed at'these elevatedt'einpemrnres which deleteriously affect the color of the resultantnaphthas. This" color cannot be removed by ordinary adsorbents, andagainthe product is unsalable. I

It has" been found that at a temperature of about or above 400 F. someof the mercaptans are converted to metalmercaptides instead ofdisulfides and as the tem perat'ure is maintained or raised to" about450 F. the metal mercaptides break down into metal sulfides and organicmono=sulfides which are non-corrosive" and s'tahle; Thisisthe t'ype ofswe'etening' reaction which is contemplated by the present invention.There is no minimum sulfur content requirement for'naphthas but, sincethey must meet the doctor test, contain no hydiogen' sulfide or freesulfur, andfpass" the" distillationcorrosion test, the amount of totalsulfur presentinthe finished product is necessarily small.Theprincipalfac' tors pertaining to the influences exerted by this"small content of sulfur compounds on thevarious' corrosion tests are theboiling point of the sulfur compounds in relation to-the boiling rangeand endpoint ofthe' naphtha, and the stability of the sulfur compoundsat moderately high temperatures. Mercaptans are rather, unstable atmoderately high temperature and break down into prod ucts corrosive tothe distillation-corrosion test. Dis'ulfides are more unstable andproduce very corrosive decomposition products, especially under theconditions present in the distillation residue. High boiling naphthaslike Stoddard solvent generally give a more corroded copper strip thanlower boiling naphthas, as' rubber solvent. Treatment ofoff-specification naphthas by prior art methods may break down thesulfur compounds into those types which are more corrosive to thedistillationcorrosion test, especially where low sulfur naphthas areconcerned since these sulfur compounds are most dif-' ficult to removeand most corrosive.

Accordingly, the present invention is primarily directed to thetreatment of naphthas or hydrocarbon mixtures containing low sulfurcontents in the order of 0.025 percent by weight or less of totalsulfur. The total sulfur may be in the form of free sulfur of sulfurcompounds or mixtures of sulfur and sulfur compounds. Crude naphthashaving more than this amount of total sulfur may be treated inaccordance with the invention but it is preferred that such naphthas bedesulfurized prior to treatment in accordance with the instant method.The 0.025 percent total sulfur may be mercaptan sulfur only and oneembodiment of the invention is directed to treating naphthas whichcontain substantially only sulfur compounds of this type. The chemicaltreatment with solid cupric acetate and basic cupric acetate or theirmixtures at 400 to 500 F., in combination with prior desulfurization asdescribed in accordance with this invention, may effect a considerablereduction in the total sulfur content of the naphthas as by as much aspercent, but generally the reaction is one of sweetening ortransformation of the sulfur compounds into non-corrosive form.

In order to demonstrate the invention, a series of experimentswereconducted in which an intermediate sweet West Texas naphtha having aboiling range of 250 to 400 F. was subjected to vaporization and passageover solid cupric acetate at a temperature of about 450 F. underatmospheric pressure and with a space velocity of 1*.0 with a percentliquid recovery. The following table makes a comparison of the sulfurdistribution in the charge stock, which gave a negative to borderlinedistillation-corrosion test, with that of the products after treatmentwith solid cupric acetate.

TABLE I Sulfur Distribution Product Percent w.:

Negative to Borderline. Positive...

Negative.

Negative.

In order to further demonstrate the invention, the following table isshown wherein various treating agents were investigated as to theirability to transform the corrosive sulfur compounds in a naphtha tonon-corrosive forms as evidenced by a good or bad distillation-corrosiontest. In'these tests, the same West Texas naphthawas used as in theprevious experiment and the same reaction conditions were used. In eachinstance, with the CXCCP tion of copper nitrate, the materials used gaveaproduct of good color. The table shows whether or not tliereha's been areduction in sulfur content and whether or not the product'passed thedistillation-corrosion test.

TABLE 11 Treatment of a naphtha with various agents at 450 F.

Copper nitrate. Copper ch1orido Active carbon"-.. Porocel (regeneratFullers earth No: Filtrol X-417 Yes No. Filtrol X-466 Yes No.

. Nickel vanadate Sea Sorb (MgO) Ammonium molybd Borax glass Sodiumbicarbonate Lithium carbonate- Molybdenum oxide Vanadium pentoxideChromie oxide In practicing the present invention, any hydrocarbonmaterial from which naphthas or solvents or similar products may beobtained can be used and subjected to treat ment with the organo coppercompounds of the present invention at 400 to 500 F. wherein theobjective is to overcome the tendency of the product toward theformation or carry-over of those types of sulfur compounds which cause apositive distillation-corrosion test. Fractionation into variousspecialty naphthas may precede or follow treatment in accordance withthe invention. To prolong the life of the treating agents, it ispreferred that the more volatile components and the high boilingresidues present be removed by fractionation. or other methods prior totreatment in accordance with the invention. For example, a crude oilcontaining from 1.0 to 3.0 or as high as 7.0 weight percent of sulfur isfractionated to obtain a wide boiling range virgin or straight-runnaphtha having an end boiling point of bout 500 F. A gas oil fractionmay be used which may boil between about 500 and 700 F. Kerosenefractions may also be used. Preferably a straight-run naphtha fractionhaving up to 0.025 percent of total sulfur and boiling between 110 and450 F. is used.

The boiling range of the particular fraction removed for treatment orafter treatment in accordance with this invention may be varied somewhatfrom the boiling ranges given depending upon the relative amounts ofspecialty naphtha, rubber solvent, V. M. & P. naphthas desired. Bynarrowing the boiling range of the virgin naphtha to within 100 to 250F., the process may be directed to obtaining rubber solvents almostexclusively.

On the other hand, by starting with a fraction boiling.

between 200 and 400 F., the process may be directed to production of V.M. & P. solvents and specialty naphthas. In one specific embodiment ofthe invention, the treatment of the entire first fraction boiling up to500 F. or more to produce a wide variety of products ranging from rubbersolvents up to high boiling specialty naphthas including, for example,petroleum ether 90140 F., Special Textile Spirits 180 210 E, LightMineral Spirits 290330 F., Stoddard Solvent 210-385 F., and High FlashDry Cleaning Solvent 360400 F., all being non-corrosive, odorless, andmeeting the rigorous requirements of the industry, is contemplated.

In treating naphtha fractions or hydrocarbon mixtures from which naphthafractions may be separated, which contain above 0.025 percent sulfur,as, for example, a naphtha containing from 0.10 to as high as 7.0percent sulfur, it is desirable to subject the naphtha to adesulfurization reaction before treatment in accordance with theinvention. For this purpose, the naphtha may be vaporized and passedover a bauxite catalyst at 700 to 800 F. .A hydrodesulfuriz'ationreaction may be em ployed if the naphtha contains a considerable portionof sulfur compounds; Treatment with such desulfurization catalysts asmolybdates, sulfides, and oxides of iron group metals and mixtures,-including cobalt molybdate, chromicoxide, vanadium oxide with molybdenaand' alumina, andsulfides of tungsten, chromium or uranium, with orwithout the presence of'hydrogen at temperatures from 500 F. to 800 F.and under pressures from 20 to pounds per square inch will eflectivelydesulfurize the naphthas' as a pretreatment. A particularly efiieientcatalyst for this purpose is cobalt oxide-molybdena-aluminaor ac'hromia-molybdena-alumina catalyst employed at about 750 F. under 250pounds pressure of hydrogen. After such treatment it is customary tosubject the naphtha to stripping at about 400 F. and 240 p. s. i. g. toremovethe hydrogen and hydrogen sulfide.

In certain instances, it may be desirable to increase the solvency ofthe naphthas produced. For this purpose, the naphthas may be firstsubjected to a mild reforming or hydroreforming operation preceding thechemical treatment with cupric acetate. The hydroreforming may beconducted using a cobalt molybdate or copper molybdate catalyst and thesour naphtha passed thereover at temperatures between 825 and 850 F. Thearomatization may be promoted by a platinum-containing catalyst at 800to 825 F. Since these processes of desulfurization and aromatization arewell known and merely used as preliminary treatments for the presentprocess, further description is unnecessary.

The contacting of naphthas with the copper treating agents in accordancewith. this invention may be effected in any suitable manner such as: byfiltration of the naphthas through towers containing the copper reagent;by mechanical agitation of the comminuted reagent with the naphtha; orby circulation of a slurry of the reagent suspended in the naphtha. Thenaphtha to be treated is heated to a temperature of about 400 to 500 F.and preferably 450 F. and the vapors passed through or in contactwiththe copper treating agent using the aforementioned techniques. Adequateconversion of the sulfur compounds to non-corrosive form may be obtainedby passing the hot liquid naphtha under pressure through the coppertreating agent. The vapor treatment is preferred because of the easewith which the reaction may be carried out. Space velocities of from 0.2to 100 may be used. Any of the well known percolation, fixed bed, orplural bed vapor-solid contact methods of the prior art may be used aslong as intimate contact is obtained at a temperature within 400 to 500F. Since the degree of treatment depends somewhat on the correlationbetween temperature and time of contact as in all such chemicaltransformations, it is usually desirable to conduct the treatment atrelatively high space velocities when temperatures above 450 F. are usedand at lower Space velocities when temperatures below 450 F. are used.In general, the space velocity is selected to give results correspondingto those obtained at a vapor space velocity in the range of about 0.2 to3.0 at 20 pounds per square inch pressure at about 450 F. Theseconditions consistently give satisfactory results.

The chemical agents used herein are available commercially or may beprepared from raw materials. Copper acetate may be formed by reacting acopper salt with acetic acid. Cupric oxide or copper hydroxide may bereacted with acetic acid to form the copper acetates. Variation in theproportions of reactants influences the production of the normal orbasic salt as desired. These copper salts may be used alone or inadmixture as contact materials.

Although the vapor-solid contact procedures constitute an expedientmethod of carrying out the invention, one preferred method is to bringthe naphtha in either liquid or vapor form into contact with a slurry ofthe copper reagent in an inert liquid. For this purpose, the inertliquid should be unreactive and be substantially free of sulfurcompounds that may upset the distillation-corrosion test. The inertliquid carrier preferably will have an initial boiling point slightlyabove the end point of the hydrocarbon mixture or naphtha being treated,and not exhibit an excessively high vapor pressure at temperaturesbetween 400" and 500 F. in order that the necessity of using excessivepressures to maintain the carrier in liquid form may be avoided. Theprocedure used in the copper oxide slurry treatment may be used.Suitable carrier liquids for the treatingagents may comprise highboiling hydrocarbons, gas oils, cracked fractions, cracked gas oil,lubricating oil distillates, residual stocks, or the various organicliquids, all of which are inert under the conditions of treatment. Thecontacting is continued until the desired degree ofsweetening iseffected, whereupon the treated product may be separated from thesuspended copper reagent either by settling or filtration.

, Upon completion of the treatment with copper acetate, the products maysometimes have a slight acrid odor. This odor may be removed by causticwash since it is due to a trace of sulfur dioxide. After treatment withthe copper acetate, the naphtha is washed free of the organicby-products by use of a Water wash and any copper sulfide by-productformed may be reclaimed by roasting at temperatures of 1100 to 1300 F.to convert this material to copper oxide. Following this, the treatingagent is subjected to reaction with acetic acid in concentrated form toreform the copper acetate. In most instances, it will be found that agiven quantity of copper acetate can be economically used for some timeto successfully treat naphthas and may be discarded to save the cost ofregeneration.

4 As an alternative procedure, the copper treating agents may be usedadmixed with an inert carrier to insure intimate contact and simplifyhandling. The treating agents may be added to such inert carriers assilica, bauxite, pumice, active carbon, alumina, etc., by simple mixingor impregnation. Although the invention has been demonstrated byspecific embodiments, the only limitations thereon appear in theappended claims.

What is claimed is: j p

1. The method of producing special solvent naphthas from highly refinedpetroleum hydrocarbon mixtures containing small amounts of total sulfurof not more than about 0.025 weight percent which comprises subjectingsaid hydrocarbon mixtures to contact with a material selected from thegroup consisting of cupric acetate and basic cupric acetate and theirmixtures at temperatures of about 400 to 500 F. and separating specialsolvent naphthas therefrom characterized by their ability to pass thedistillation-corrosion test.

2. The method in accordance with claim 1 in which the contact materialis cupric acetate.

3. The method in accordance with claim 1 in which the contact materialis basic cupric acetate.

4. The process in accordance with claim 1 in which the contacting iscarried out at a temperature of about 450 F., at substantiallyatmospheric pressure, and with a space velocity of about 1.0.

5. The method in accordance with claim 1 in which the contact materialis cupric acetate supported on an inert carrier in an amount such thatthe copper content of the total mass is less than about 10 per cent.

6. The method in accordance with claim 1 in which the contact materialis basic cupric acetate supported on an inert carrier in an amount suchthat the copper content of the total mass is less than about 10 percent.

7. The method in accordance with claim 1 in which said highly refinedpetroleum hydrocarbon mixtures are obtained by catalytic desulfurizationof hydrocarbon mixtures containing a high content of sulfur compounds inthe presence of a desulfurization catalyst at a temperature of about 700to 800 F.

References Cited in the file of this patent UNITED STATES PATENTS1,768,683 Gray July 1, 1930 1,825,861 Gray Oct. 6, 1931 2,467,429 HooverApr. 19, 1949

1. THE METHOD OF PRODUCING SPECIAL SOLVENT NAPHTHAS FROM HIGHLY REFINEDPETROLEUM HYDROCARBON MIXTURES CONTAINING SMALL AMOUNTS OF TOTAL SULFUROF NOT MORE THAN ABOUT 0.025 WEIGHT PERCENT WHICH COMPRISES SUBJECTINGSAID HYDROCARBON MIXTURES TO CONTACT WITH A MATERIAL SELECTED FROM THEGROUP CONSISTING OF CUPRIC ACETATE AND BASIC CUPRIC ACETATE AND THEIRMIXTURES AT TEMPERATURES OF ABOUT 400 TO 500* F. AND SEPARATAING SPECIALSOLVENT NAPHTHAS THEREFROM CHRACTERIZED BY THEIR ABILITY TO PASS THEDISTILLATION-CORROSION TEST.